A076055 Composite numbers which when read backwards are primes.

14, 16, 20, 30, 32, 34, 35, 38, 50, 70, 74, 76, 91, 92, 95, 98, 104, 106, 110, 112, 118, 119, 124, 125, 128, 130, 133, 134, 136, 140, 142, 145, 146, 152, 160, 164, 166, 170, 172, 175, 182, 188, 194, 196, 200, 300, 301, 305, 310, 316, 320, 322, 325, 328, 332

Offset

1,1

Comments

If m is a term, then 10*m is another term. - Bernard Schott, Nov 20 2021

Links

Michael S. Branicky, Table of n, a(n) for n = 1..10000

Mathematica

Rev[n_]:=FromDigits[Reverse[IntegerDigits[n]]]; Select[Range[332], !PrimeQ[#] && PrimeQ[Rev[#]]&] (* Jayanta Basu, May 01 2013 *)

Prog

(Python)
from sympy import isprime
def ok(n): return not isprime(n) and isprime(int(str(n)[::-1]))
print([k for k in range(333) if ok(k)]) # Michael S. Branicky, Nov 20 2021

Crossrefs

Cf. A076056.

Intersection of A002808 and A095179.

Sequence in context: A217707 A176686 A007935 * A068653 A225193 A102616

Adjacent sequences: A076052 A076053 A076054 * A076056 A076057 A076058

Keyword

base,nonn

Author

Amarnath Murthy, Oct 04 2002

Extensions

Corrected and extended by Sascha Kurz, Jan 20 2003

Status

approved